1. Field of the Invention
The present disclosure generally relates to well cementing, and more particularly to ultra low density cement compositions for use in wellbore servicing.
2. Background of the Invention
Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore down to the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe, e.g., casing, is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the pipe and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, primary cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the string of pipe to the walls of the wellbore and seal the annulus. The main objectives of primary cementing operations include zonal isolation to prevent migration of fluids in the annulus, support for the casing or liner string, and protection of the casing string from corrosive formation fluids. Subsequent secondary cementing operations may also be performed. Secondary or remedial cementing operations are performed to repair primary-cementing problems or to treat conditions arising after the wellbore has been constructed.
Due to various wellbore conditions, there are often needs for slurries with wide-ranging densities. For example, if the formation has a low fracture gradient, a low density slurry is needed to perform water shutoff and other standard cementing operations without fracturing the formation and causing loss circulation problems. It is also desirable for the slurry to transition from the flowable (slurry) state to the solid state in a predictable and rapid manner to allow placement of the slurry and to minimize invasiveness.
A particular challenge in cementing is the development of compressive strength in a cement slurry with an ultra low density. Thus, a need exists for cement compositions that rapidly develop compressive strength at ultra low densities.